In order to achieve the best possible sawing results with jigsaws, it has been known for a long time that the vertical up and down movement of the saw blade should simultaneously have superimposed on it a horizontal back and forth movement. With these so-called reciprocating stroke jigsaws, significantly better sawing performance can be achieved as a result of the improved chip removal, particularly in the case of greater material thicknesses.
For the creation of this reciprocating stroke movement, reciprocating stroke drive mechanisms are known which require a large number of moving parts. Thus, from DE 37 02 670 A1 a reciprocating stroke drive mechanism is known in which the stroke movement of the slide which holds the saw blade and which is guided in an upper and a lower beating is created by means of a Scotch-yoke mechanism. The upper bearing of the slide is placed along with the latter inside the saw housing in such a way that it can rotate, while the lower bearing of the slide is guided so that it can move both cross-wise, in the direction of the plane of the saw blade, as well as in a swivelling manner inside the saw housing. For the up and down movement, a guiding connecting link, which is a component of a stroke element, is actuated. In conjunction with that, the stroke element is guided in a sliding manner in a straight-line guide. The lower end of the stroke element acts on one arm of a bell-crank lever, which can rotate around a bearing that can be manually adjusted in the direction of the axis of the slide. The other arm of the bell-crank lever is tangent to the lower slide bearing, which can be displaced in a limited manner cross-wise to the longitudinal axis of the slide against the force of a spring. In this way, a cross-wise movement is superimposed on the slide which is moving up and down, so that the slide carries out a periodic reciprocating stroke movement.
What is disadvantageous about this type of reciprocating stroke drive mechanism is the fact that a very large number of moving parts are required. Thus, along with an upper slide bearing, it is also necessary to have a lower slide beating in which the slide is guided in sliding manner. The lower slide bearing is in turn guided in a complex manner, so that it can move both cross-wise in the direction of the plane of the saw blade as well as in a swiveling manner inside the saw housing. Finally, the stroke element for the actuating of the bell-crank lever also has to be guided in a straight-line guide in a sliding manner. As a result of the large number of moving parts and, in particular, the large number of bearing arrangements, the entire assembly is prone to failure, difficult to manufacture and assemble, and thus expensive as well.
The task of the present invention is to eliminate the mentioned disadvantages, and to further develop a reciprocating stroke drive mechanism for jigsaws in such a way that, using as few moving parts, beatings, etc. as possible, an optimal reciprocating stroke movement of the saw blade is created, which means one that works in a trouble-free manner and is simple to create.